According to a number of studies, people with higher incomes are much more likely to (rather smugly) say that getting rich is primarily almost solely on hard work than people who have lower incomes.

Yet when I congratulated Venus Williams on her tennis (and business) success, she looked uncomfortable. “I work hard but I’m really lucky. My parents, my sisters, the people who have helped me… I’m really lucky.”

When I smiled and said to Mark Cuban, “All the things you’ve done? You’re my hero,” he looked uncomfortable. “I’m no one’s hero. I work hard… but I’m also really lucky.”

When I told Richard Branson I admired the way he constantly tries new things, he looked uncomfortable. “I am willing to take risks… but when they work, it’s really not because of me. I’m just lucky to be surrounded by so many great people.”

Why do so many people feel success is based solely on their own hard work, intelligence, and grit… and relatively few are willing to admit that luck played a role?

And why does that make them, well, borderline insufferable?

One Problem: Hindsight Bias

In part, denying the role of luck is due to hindsight bias: The tendency to feel that an event, after it happens, was predictable. That every plan was perfect, every vision clear, every step flawlessly executed.

In this case: If I get rich, the qualities I possess — that the things I did — are what made me rich.

That feeling is understandable. If you’ve worked hard, you remember all those nights and weekends. If you overcame challenges, you remember all those obstacles and roadblocks. If you made smart choices, you remember all the analysis and evaluation — and you especially remember the judgment calls where intuition and experience, rather than just data, guided your decisions.

All of which leads you to believe that it was you — just you — that caused your success.

Which is never, ever true. And not only that, but…

Acknowledging the Role of Luck Can Make You a Better Person

Venus is smart and hardworking… and also lucky enough to have had parents with genuine vision.

Sir Richard is smart and hardworking… yet if a flight home had not been canceled might never have started Virgin Airlines.

Cuban is smart and hardworking… yet as he says, “Life is half random. Being a billionaire requires a lot of luck, a lot of great timing.”

Which is a good thing: Research shows people who recognize luck — who recognize that external forces outside of their control contributed to their success — also tend to feel more gratitude.

And are more generous.

That’s why recognizing the role luck played in your success is so important. Hard work, intelligence, perseverance, determination, experience… all those qualities, and more, contribute to success.

In fact, those qualities are foundational to success.

When you recognize the role luck has played in your success, you’ll be more humble. More grounded. More understanding of others. More likely to step in, step up… and be the person that helps give someone else their lucky break.

Because you’ll appreciate the fact that along the way… you were lucky that people helped you.

The opinions expressed here by Inc.com columnists are their own, not those of Inc.com.